Environmental Engineering Reference
In-Depth Information
2.
M
ATERIALS AND
M
ETHODS
2.1. Plant Materials, Growth Conditions and Treatments
The ecotypes of the soybean adopted in this study were salt-sensitive
G. max
ZH13
cultivar and the salt-tolerant
G. soja
BB52. The ZH13 was widely cultivated in China and
provided by Shandong Academy of Agricultural Sciences, while the BB52 was collected
from Yellow River Delta, Shandong Province, China.
The homogeneous, full and unbroken seeds were collected and sew in medium for
germination. The medium was laid with two layers of filter paper which were moistened with
Hoagland nutrient solution. Firstly the seeds were fostered at 25°C for 5 d in the darkness and
then the young seedlings were transferred to the plastic pots filled with vermiculite for further
development in artificial climatic chambers (Huier, China). The plants were cultivated under
12h light/12h dark with 25/18
℃
respectively. The humidity of the climatic chambers was
kept at 65%.
The salt treatments with different NaCl dosages were applied to the plants in seedling
stage and mature period respectively. Plants with uniform growth pattern were selected for
treatments.
The salt treatments were carried out by irrigating Hoagland solution including 0, 50, 100,
200 or 300 mM/L NaCl and sustained for 7d. The higher NaCl concentrations (>50 mM)
were imposed incrementally to the final concentration by 50mM step every day. The samples
were harvested after treatments and preserved in -80
℃
for measurement. Each treatment had
three biological replications at least.
2.2. Measurement of Water Potential (ψ
w
)
The instrument used in this experiment was WP4-T Dewpiont PotentiaMeter (USA) and
the principle of the measurement was chilled-mirror dew point technique. The leaf and root
samples were sipped up and placed in a sample cup. It should be noticed that the sample cup
should be covered completely.
2.3. Measurement of Relative Water Content (RWC)
The leaf and root samples were harvested and weighted (fresh weight, FW). Then the
samples were soaked in deionized water at 4
℃
for 24h and weighted (saturated fresh weight,
SFW) after blotted up. Finally, the samples were killed out at 105
℃
for 30 min and stovinged
at 80
℃
for 48h. The remaining weight was the dry weight, DW. RWC was calculated as:
RWC= (FW-DW) / (SFW-DW). The specific procedures of the RMC measurement referred
to Flexas et al. (Flexas et al., 2006).
